Avantages
The working hours are very reasonable -- generally, the management makes realistic schedules. The company dominates its niche, so its product probably isn't going to vanish as it might at a startup. The software development process is quite mature, which does help you do your best work.
Inconvénients
Like another review stated, the organization is flat -- there is a smaller chance of advancement here than at fast-growing companies. The product features are not exactly cutting edge, mostly because their customers have been around for decades in a highly regulated industry and thus don't like changes. You may not be working on the latest and greatest technology. The management requires employees to work 45 hours per week, which is very draining for those who have hour-long commutes into Chicago.